Stair protractor



Dec. 1, 1,931. w. H. DREscHER STAIR PROTRACTOR Filed Oct. 29, 1928 Patented Dec. 1, 1931,v

narran stares smaila ritornaVoiron ifY Y i Application inea october eefiasf'sriai:no. classe.

The present invention relates to stair protractors and embodies an improved form of protractor for laying out stairs of any desired pitch, as well as providing a means for laying off the banisters without readjustment of the protractor. t is contemplated that the protractor may be used to lay on' stairs upon stringers of considerable width and provision is made to accommodate conditions 1o of this character as well as to permit the step and riser marking to be made at .any point in the depth of the Stringer. After an initial setting of the instrument,'there is no need for further adjustment as long as the step and v riser relationship of a stairway remains constant. By the construction provided herein, the protractor is easily and securely adjusted, no particular skill being required to effect the adjustment.

The invention will .be understood more fully in connection with the accompanyingvv 4 4 of Figure l, and looking in the direction of the'arrows.

Referring to the above drawings, adesignates a plate formed with sides a and a2 in ninety degree relationship, the lengths of these sides being immaterial. PreferablyV Y 1. 0 scales are inscribed upon these sldes, theV scales starting from the intersectiony thereof and extending to the diverging ends as clearlyshown in Figure l. A rounded head portion a3 is formed at the intersection of the sides, the center of the rounded portion lying in the intersection thereof. The rounded head portion vis provided with an aperture at through which a pivot pin a5 passes.

An arm o is formed with a rounded socket portion b which fits over the rounded head f pivot pin a5. f Apertures d and e are formed in the sides a3 and is formed aperture b2 uthrough which thepivot pin c5 extends. In this man- 'ner,"th'ei arnro is pivoted so that the axis thereof'passes throughthe pointv of intersecl Y l tion of the lsides al and a2. thumb nut b3 is *55 provided to 'secure the arm to the pivot pin 0 5 and a second thumb nut c, engaging pin c, is

Vtightened to securethe arm yin a desired position". Thev pin o rides 1n va slot a6 which is formed as, an arc", the vcenter ofwhich is the '"Co of'theyplate aand cooperate with apertures d" and e', respectively, to form a square of j the protractor'.e vvByremoving the pin c -from "U65 1 the slotdG and'inserting it through apertures Z and Zorc and e', respectively, a;V square may be formed of the instrument.

, A stop f, formed of an angle iron f3 may be-secured-to the arm Z2 to permit the protractor to be` used from the opposite side of the Stringer. The stop 7 permits the protractor to be used from the other side of the stringer since its flanges may be adjusted so4 that it is parallel tothe side of the stringer 'f5 with the arm in such position that the edges a and 0:2 are at the desired angle of step and riser. In this manner, the protractor l may be held against the opposite side of the Stringer by stop f and the desired angles drawn. Wing nuts f and plate f2 serve to clamp the stop to the arm Z2 as clearly shown in Figure 3. As an additional feature, la hole g is formed in the arm at such distance from the aperture through which the pin o passes, that the last mentioned aperture may be used in conjunction with the pivot pin a5 while the pin c is used in conjunction with the aperture g to lengthen that portion of the arm Z) which extends outwardly from the 90 lintersection of the sides a and a2.

This pro'- vides a means for marking olf stairs upon stringers of unusual depth.

It will be apparent that the protractor described above is capable of yuse with a given stair pitch without necessitating more than one adjustment. The initial adjustment may be made with great facility by applying a square to one side of the plate, as shown in,...v Figure l, and adjusting the arm so that the lower edge thereof falls upon suitable points on the scales of the arms of the square to give the step and riser dimensions. For example, with the square as applied as in Figure l, the lower edge of the arm is set on the calibrations 5 of the vertical portion of the square and 8 of the horizontal portion, thus indicating the adjustment of the protractor for laying off stairs, the steps and risers of which are 8 and 5, respectively. As will be quite apparent, the protractor is capable of use in connection with constructions of many specialized forms and the invention is not to be limited, save as defined in the appended Y claim.

I claiin as my invention: l

"A protractor comprising a plate having two edges intersecting at right angles and being straight throughout the lengths there of, a rounded head formed on the plate with the point of intersection of the outer edges as the center thereof, an arm extending bey'ondv the plate on both sides of the head, means to pivot the arrn to the head at a point lying in the median plane of the arm and the point of intersection of the edges, means to secure the arm to the plate ina desired position, an adjustable stop on the arm, and

means to secure the stop at a desired angle with respect to the median plane of the arm.

`This specification signed this 27th day of October, A. D. 1928. Y

VWILLIAM HENRY DRESGHER. 

